Race 32 (Lawnmower Racing)

posted by Jordan Peterson on Sun, 03/28/2010 - 09:54

UPDATE: NEW RACE 32 MOWER BUILDS COMING SOON!

BUILD #2, Hadlock Days 2010: On Saturday, a group arrived with an electric mower that runs on a bank of lithium iron phosphate batteries and uses an electric motor instead of an internal combustion engine. Read more... -- Peninsula Daily News

2010 ARMA Rulebook, ARMA Web site

Event Schedule • Hadlock Days •Journal Entries • More Electric Vehicles • Racing List • Sponsors

 

Welcome to Race 32, where Bob Mills and Jordan Peterson get together to build a Craftsman Electric Riding Lawnmower, taking part in this year's 2010 Hadlock Days Lawnmower Race and Super Stock Lawn Mower Racing Association events. We've got a growing list of sponsors, lots of real estate left for advertising, and a need to go faster! If you'd like to get your business on 32, email sponsor32@race32.com.

Sponsors

Old News: Build #2 Journal, (See Bob's new build, See Jordan's new build)

2010-07-10: Today Nora raced Powder Puff Class in the Hadlock Days Lawnmower Races. Needed faster chargers, as racing was limited to how fast we could get back on the track. Belt broke in lap 4 of first race. Spindle and wheel hub replaced. Secondary belt replaced.

2010-05-14: Yesterday we mounted the hood cover and front bumper skirting. Performance wise, our takeoff power is substantial, but top speed is limited to around 20 MPH. Halving the size of the transmission pulley should increase our speed. Additionally, we need a stiffer spring on the clutch idler pulley, and a new disc pad on the rear brake, as our sacrificial test pad broke down too quickly.

2010-05-13: After getting version 2 of version 1 kart together, and the controller still set at 20% output, Bob Mills takes a ride. Yeah, the kart is unfinished, but with our new motor, voltage increase, and high amperage controller additions, we were excited to see what would happen.

2010-05-1: We've redone some of our frame structure and drive train.

  • New design of front steering assembly, including axle, wheel spindles, and tie rod actuation and mechanical wheel turn radius separation
    • Lowered front end
    • Lowered rear seat and wheel fenders
    • Widened front axle
  • New high power motor, controller & electric contactor
    • New 48-72 volt wound motor
    • New 650 amp, programmable controller with plug braking
    • New higher amp rated electric contactor
  • A slight change in voltage: From 24 volts to 48
    • 2 more group 27dc batteries, now a total of 4
    • New battery boxes and exterior framework being made

2010-04-20: As you can see from the previous videos, the kart is doggy. What we're looking for is one thing: Dangerously fast enough to leave an EV Grin from ear to ear after getting off the kart. That doesn't seem too impossible.

Broken Parts: Our manual contactor switch wasn't heavy enough to handle the loads and welded itself perminently closed. Yes, we knew it wouldn't handle it. We've got a new 2 stage solenoid to install and wire up some sort of key switch and emergency disconnect should the kart get out of control, and or the rider falls off.

Since 1 controller, then 2 controllers in parallel didn't do the job, we're thinking the controllers just aren't a good match for the motor we're using. Since we want more control of the drive system, we picked up an Alltrax AXE 4865P controller. Even though we know we'll end up going 48Volts on the battery pack, we'll be installing the Alltrax today and doing a test run with the existing 24Volt battery setup. Last night, we downloaded the Alltrax software and programmed the controller to limit max amps to 50%, which would be around 325 Amps. Yes, we're really not sure how much torque a craftsman riding lawnmower transmission will take.

Thanks to Solar Motive, located in Port Townsend, WA, we scored a 40 Amp 24 Volt charger that will help in faster charging times.

Additions:

  • Changing out the Kinetek controllers with one Alltrax AXE 4865 made a huge difference in accelleration. Top speed has not been altered at this time as neither the motor, voltage or gear ratios have been messed with. Having an Alltrax programmable controller has provided our project with a wide range of performance to offset mechanical disadvantages. For instance, belt slippage on our drive system can be adjusted within the controller for softer starts. The same in throttling down. We have the plug brake model of the AXE 4865, but have not hooked it up yet.
  • 500 Amp shunt and meter installation on the negative battery leg. Now we can see what we're drawing.
  • In our test driving with the Alltrax and prior controllers, we noticed exessive heat buildup in the cast iron motor, particularely in the positive pole. With the kart in 5th gear, taking off from as standstill draws over 500 Amps; assuming 600 Amps are being drawn (100 Amps over our shunt meter setup) that's roughtly 20 horsepower. However, our guess is the windings in the motor are burnt or the brush assembly toasted, as our take-offs didn't feel anything like 20 HP. We've eaten the cost of a controller, but a motor being sponsored to our project would keep our development on the roll.

Things to fix:

  • Front steering getting over center and locking in the right turns, especially when the front right wheel is at a higher elevation from the rest of the kart.
  • Full motor replacement. It's heavy, doesn't cool easily, and at this time, inefficient.

Build #1